Method and apparatus for testing an aperture board in a high speed printer

ABSTRACT

A test system for detecting the presence of an obstructed aperture in an ink mist type printer is disclosed. The ink mist type printer operates on the principle that an ion stream modulated by an aperture board according to the pattern of the character to be printed, charges the ink mist, which is then attracted by an electric field to the surface of the paper. If an aperture of said aperture board is obstructed a portion of the printed character will not be evident. In order to detect the aperture, a conductive board is inserted between the aperture board and the paper, and an amplitude and/or pattern of an electric current in the conductive board due to the ion stream shows the presence and location of the obstructed aperture.

United States Patent [191 Watanabe et al.

[ METHOD AND APPARATUS FOR TESTING AN APERTURE BOARD IN A HIGH SPEEDPRINTER [75] Inventors: Akinori Watanabe; Katsuhide Tanoshima, both ofTokyo, Japan [73] Assignee: Oki Electric Industry Co., Ltd., Tokyo,Japan [22] Filed: July 26, 1974 [21] Appl. No.:, 492,340

[52] US. Cl. 324/33; lOI/DIG. 13; 324/71 EB [51] Int. Cl. G01N 27/60[58] Field of Search 324/33, 71 R, 71 EB;

10l/DIG. 13

[451 Sept. 16, 1975 Primary ExaminerAlfred E. Smith AssistantExaminerWm. H. Punter Attorney, Agent, or FirmLewis H. Eslinger; AlvinSinderbrand 57 ABSTRACT A test system for detecting the presence of an0bstructed aperture in an ink mist type printer is disclosed. The inkmist type printer operates on the principle that an ion stream modulatedby an aperture board according to the pattern of. the character to beprinted, charges the ink mist, which is then attracted by an electricfield to the surface of the paper. If an aperture of said aperture boardis obstructed a portion of the printed character will not be evident. Inorder to detect the aperture, a conductive board is inserted between theaperture board and the paper, and an amplitude and/or pattern of anelectric current in the conductive board due to the ion stream shows thepresence and location of the obstructed aperture.

4 Claims, 5 Drawing Figures METHOD AND APPARATUS FOR TESTING AN APERTUREBOARD IN A HIGH SPEED PRINTER BACKGROUND OF THE INVENTION The presentinvention relates to a method and an apparatus for testing an apertureboard.

The operational speed of an information processing system including acomputer system has recently been improved, thus requiring the use of ahigh speed peripheral device including a printer. A conventional highspeed printer is a line printer with a type drum or a type train.However, this line printer has many disadvantages, some of which arethat the operational speed is not enough for the latest informationprocessing system, high level of noise and/or limitation of the numberof printing types. In order to overcome these disadvantages of the priorline printer, some high speed printers with new operational principleshave been developed. Among them, one of the most promising is an inkmist type printer. The ink mist type printer operates at high speed.i.e. 8,000 lines per minute, with a low noise level. Further, it cantype not only alphanumeric characters but also Chinese or Japanesecharacters.

The operational principle of an ink mist type printer is that an ionstream generated by corona discharge passes through apertures of anaperture board and ionizcs an ink mist, and the movement of theelectrically charted ink mist is acceleratedby a negative electrode andis attached to paper according to the pattern of characters.

The disadvantage of the prior ink mist type printer is that the ink mistobstructs apertures of the aperture board and prevents the passages ofthe ions. The obstructed apertures create incomplete printed characterswith missing portions and the source of the trouble cannot be locateduntil the printing operation is actually performed. Therefore, bothpaper and operational time are wasted.

SUMMARY OF THE INVENTION The general purpose of the present invention isto provide an ink mist type printer with a facility, for testing thepatency of apertures.

It is an object, therefore. of the present invention to overcome thedisadvantages of the prior ink mist type printer by providing a methodof testing an aperture board if apertures are obstructed.

It is also an object of the present invention to provide an apparatusfor testing an aperture board if apertures are stopped up. According tothe present invention, a conductive board is inserted between theaperture board and the paper and an amplitude and/or pattern of anelectric current on the conductive board due to the ion stream shows thepresence of an obstructed aperture, since the ion stream cannot gothrough the aperture.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects,features, and attendant advantages of the present invention will beappreciated as they become better understood by reference to theaccompanying drawings wherein:

FIG. 1 shows (the explanatory) sectional view of a conventional ink misttype printer;

FIG. 2 shows a sectional view of an ink mist generator in theconventional ink mist type printer;

FIG. 3 shows a perspective view of a conventional aperture board;

FIG. 4 shows a block diagram of a test device according to the presentinvention; and

FIG. 5 shows the detailed structure of the conductive board of FIG. 4.

v DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, theoperational principle of an ink mist type printer will be explained toprovide a basis for under standing of the present invention.

FIG. 1 shows a basic structure of an ink mist type printer. Theprinciple of typing in an ink mist type printer is to attach an ionstream to an ink mist which types or draws characters on printing mediumlike a sheet of paper. Said ion stream is controlled by an electricfield on an aperture board according to the pattern or shape of printedcharacters. In FIG. I, an aperture board 1 is positioned between apositive electrode 6 and printing medium 7. The printing medium 7 isjust ordinary paper. A negative electrode 8 is provided hehind theprinting medium 7 and doubles as a platen. The positive electrode 6 isstraight and has a sharp point. Several thousand volts applied to thepositive electrode 7 generates a corona discharge and an ion stream 9.

The strength of the electrical field required for corona dischargedepends upon the shape of the positive electrode 7 and is generally1000l300 V/mm. The movement of the ion stream 9 generated on thepositive electrode 7 is accelerated by the negative electrode 8 andpasses through apertures 2 of the aperture board 1, the structure ofwhich is shown in detail in FIG. 3, wherein reference number 3 is adielectric layer, and 4 and 5 are conductive layers. The conductivelayers 4 and 5 are separated by a plurality of cells shown as 5a, 5b,5c, and each cell 5a, 5b, 5c, is insulated from the others. A voltage Eis applied to each cell of the conductive layers 4 and 5, and thedistribution of voltage E is related to the pattern or shape of the character to be printed. An electric field generated in the apertures bysaid voltage E prevents or accelerates the passage of the ion streamaccording to the polarity of the voltage E, therefore, the density ofthe ion stream which comes out of the aperture board I is modulatedaccording to the pattern of the character. Voltage E is supplied by acharacter generator (not shown).

There is an ink mist between the aperture board 1 and printing medium 7.The ion stream 9 modulated by theaperture 1 attacks and charges theparticles of the ink mist, then, the charged particles 10 of the inkmist are accelerated by the negative electrode 8 and attach to thesurface of the printing medium 7. Thus. the pattern of the character isprinted on the printing medium in ink.

FIG. 2 shows the structure of an ink mist generator, which comprises anink tank 20 containing, ink 21. an ink inlet 22, an ink outlet 23, andultrasonic wave exciters 24. The depth of the ink 21 in the ink tank 20is maintained automatically at a desirable depth by the ink streamthrough the inlet 22 and the outlet 23. The cxciters 24 generateultrasonic waves and generate ink mist 10, the diameter of which is 5-20;1.. The ink mist 10 is transported by an air stream 25 to an ink guide17 (FIG. 1), and the ink mist 10 is directed along arrow Y in the samedirection as the movement of the paper 7.

The moving speed of the ink mist is almost the same as that of the paper7. The ink mist which is not used for printing isgathered and condensedin a tank (not shown).

One problem of an ink mist type printer is, as explained before, thatapertures of the aperture board are sometimes obstructed by ink mist,thus creating missing portions in the printed character.

FIG. 4 shows a block diagram of an apparatus for testing the patency ofapertures. In FIG. 4, the same reference numbers refer to the samemembers as those of FIG. 1. A conductive board 11 is inserted,vertically movable, between the aperture board 1 andthe paper 7. Theconductive board 11 is connected electrically to the input of anamplifier 12, the output of which is, in turn, connected to a waveformshaping circuit 13. The output of the waveform shaping circuit 13 isapplied to a memory 14. On the other hand, each cell of the conductivelayer 5 is connected to an output of a drive circuit 15, the input ofwhich is connected to the output of a selection circuit 16. Since thereare a plurality of cells on the conductive layer 5, there must beprovided a plurality of drive circuits 15, however, only onerepresentative drive circuit is shown.

In a test operation, the conductive board 11 is inserted between theaperture board 1 and the printing medium 7 by a drive mechanism shown inFIG. 5. The selection circuit 16 in FIG. 4 scans and selects aparticular cell on the conductive board 5 in a predetermined order. Thedrive circuit 15 generates an electric field in an aperture in theselected cell in the direction of the negative electrode 8. Accordingly,if the selected aperture is not obstructed, an ion stream generated onthe positive electrode 6 passes through the selected aperture to theconductive board 11, in which a small current flow is created. The smallcurrent is amplified by the amplifier l2 and its waveform is shaped bythe shaping circuit 13. The output signal of the shaping cir cuit 13 isa digital signal,- which is stored in a particular address of the memory14. The selection of the address of the memory 14 is synchronized withthe selection of the cell on the conductive layer 5 by the selectioncircuit 16. However, if the aperture is obstructed a current does notflow in the conductive board 11, thus the digital signal zero, insteadof one. is stored in the memory 14. Therefore, in the memory 14 theaddress which stores zero information shows the position or address ofthe obstructed aperture.

Many modifications of the embodiment of FIG. 4 are possible to thoseskilled in the art. For instance, all cells on the conductive layer 5may be selected at the same time and in that case, the level oramplitude of the current in the conductive board 11 indicates if thereis an obstructed aperture. Further, when no cell on the conductive layer5 is selected, the presence of the current on the conductive board 11shows that there is something wrong with an aperture.

FIG. 5 shows a drive mechanism of the conductive board 11. In FIG. 5,the conductive board 11 can move, as indicated by arrow B, verticallyalong the left guide 30a and the right guide 30b. The movement of theconductive board 11 is restricted by the upper stopper 34 and the lowerstopper 35. The arm 11a extends from the end of the conductive board 11to the plunger magnet 31. A pair of leads 32a and 3212 from the plungermagnet 31 are connected to the direct current source (not shown). Thespring 33 pulls the conductive board l 1 downwards. When the plungermagnet 31 is not energized, the conductiveboard 11 is pulled by thespring 33 until the lower end of the board 11 reaches the lower stopper35. In that condition, the conductive board 11 does not prevent theoperation of the ink mist type printer. On the other hand, when the inkmist type printer is tested, the, plunger magnet 31 is energized throughthe pair of leads 32a and 32b and the plunger magnet 31 attracts the arm11a in the direction of arrow A and lifts the conductive board 11against the tension of spring 33 till the upper end of the conductiveboard 11 reaches the upper stopper 34. In that condition, the conductiveboard 11 is between the aperture board 1 and the printing medium 7, andthe printing operation can no longer be performed, but the testoperation, explained above, is carried out instead.

As previously explained, according to the' present invention, anaperture board is tested and the address of the obstructed aperture isfound by a simple apparatus. One effect of the present invention is thatprinting paper is not wasted due to obstructed apertures.

It can be seen that the present invention provides a simple and uniquesystem for testing an ink mist type printer and although it has beendescribed with respect to embodiments, it need not be so limited, aschanges and modifications may be made which would fall within the scopeof the invention as defined by the appendant claims. I

Finally, reference numbers used in this specification are listed below.

I aperture board 2 aperture 3. dielectric layer 4. 5. conductive layer6. positive electrode 7 printing medium 8. negative electrode 9 ion It).ink mist l l conductive hoard l la. arm 12. amplifier l3. shapingcircuit I4. memory 15. drive circuit 16. selection circuit l7. ink guide20. ink tank 2 I. ink ink inlet 23. ink outlet 24. ultrasonic waveexciter 25. air stream 3()a,3()b. guide 3 l plunger magnet 3211.321).lead 33. spring 34. upper stopper 35. lower stopper What is claimed is:

1. In the method of testing an ink mist type printer comprising meansfor generating an ion stream, an aperture board having a plurality ofapertures for modulating said ion stream and charging an ink mistflowing in front of the aperture board according to the pattern ofcharacters to be printed, and printing medium arranged parallel to theflow of said ink mist for printing characters by attracting the chargedink mist. theimproved step of inserting a conductive board between saidaperture board and said printing medium for de tecting the presence ofan obstructed aperture by measuring the electric current created by theion stream in said conductive board.

2. The method of testing an ink mist type printer as claimed in claim 1,wherein a plurality of said apertures are scanned for locating theaddress of the obstructed aperture on said aperture board.

3. An ink mist type printer comprising means for generating an ionstream, an aperture board having a pluan electric current in saidconductive board for detecting the presence of an obstructed aperture.

4. An ink mist type printer according to claim 3,

wherein said conductive board is pulled downwards by means of a springand upwards by means of a plunger magnet.

1. In the method of testing an ink mist type printer comprising meansfor generating an ion stream, an aperture board having a plurality ofapertures for modulating said ion stream and charging an ink mistflowing in front of the aperture board according to the pattern ofcharacters to be printed, and printing medium arranged parallel to theflow of said ink mist for printing characters by attracting the chargedink mist, the improved step of inserting a conductive board between saidaperture board and said printing medium for detecting the presence of anobstructed aperture by measuring the electric current created by the ionstream in said conductive board.
 2. The method of testing an ink misttype printer as claimed in claim 1, wherein a plurality of saidapertures are scanned for locating the address of the obstructedaperture on said aperture board.
 3. An ink mist type printer comprisingmeans for generating an ion stream, an aperture board having a pluralityof apertures for modulating said ion stream and charging an ink mistflowing in front of the aperture board according to the pattern ofcharacters to be printed, and printing medium arranged parallel to theflow of said ink mist for printing characters by attracting the chargedink mist, characterized in that said ink mist type printer furthercomprises a conductive board vertically movable between said apertureboard and said printing medium, means for applying an electric field tothe selected apertures and means for measuring an electric current insaid conductive board for detecting the presence of an obstructedaperture.
 4. An ink mist type printer according to claim 3, wherein saidconductive board is pulled downwards by means of a spring and upwards bymeans of a plunger magnet.